JP7184523B2 - Circuitry for actuating at least one relay - Google Patents

Description

The present invention relates to a circuit arrangement for actuating at least one relay, the circuit arrangement comprising a power supply capable of supplying an actuating voltage to said at least one relay, wherein the actuating voltage and ground, an electronic switch, a relay coil of at least one relay, and a shunt resistor are electrically connected in series; A current control device capable of being controlled by modulation and configured to be capable of controlling a control current through the relay coil is included.

Relays are known as electromagnetic switches. Such relays are known from the prior art in various embodiments, are suitable for various technical applications, and can be used, for example, in safety switching devices. A relay includes a ferromagnetic core and a relay coil, the relay core being connected to circuitry from which a control current can be supplied. Furthermore, the relay includes a moveable ferromagnetic anchor and one or more relay contacts coupled to the anchor. During operation, a current flows through the relay coil, which in turn produces a magnetic flux that passes through the ferromagnetic core. This attracts the anchor and turns on the relay contacts associated therewith. The anchor is coupled with a return spring configured to move the anchor to the exit position by spring force when the control current is removed from the relay coil. In practical applications, a distinction is made between so-called closed circuit relays and shunt relays. A closed circuit relay is in the closed state, where current flows through the relay coil and the anchor is attracted. Closed-circuit relays allow monitoring of, for example, power outages or line breaks. In contrast, a shunt relay carries no current when it is closed.

Safety switching devices are today determined according to the IEC 1131 standard for differential voltages from 24 V+10% (so-called surge voltage) to 24 V-15% (so-called undervoltage). Therefore, in case of undervoltage, the operating voltage is 24V-15%=20.4V. The electrical switch of the safety switching device utilizes a conventional relay and operates with a relay voltage of 18V to 20V.

A fundamental drawback of relays is that they are relatively sensitive to shock, vibration and other vibrations. In case of undervoltage, safety switching devices provided with at least one intermediate safety relay shall be equipped with switching technology so that the relay contacts cannot open, taking into account all possible shocks, shakes and vibrations. It is necessary to be For this purpose, a high electrical holding force is required, which allows a sufficiently large force to be set aside, so that the anchor of the relay contacts, even in the event of swaying, will remain stable. It can remain in the closed position.

For a typical operating voltage of 24V, this higher voltage will cause more current to flow through the relay coils, resulting in a higher electrical holding force. In the case of an overvoltage of 24V+10%=26.4V, a somewhat higher current will also flow through the relay coils, thus causing a loss of power and generating a great deal of heat.

In the case of large technical installations with long feed lines, a higher voltage is usually set, so that even an electric user connected at the final end of the technical installation is not undervoltaged. In this switch cabinet, unless readjusted, there is a slight overvoltage resulting in significant heat loss caused by higher currents. A current control device can be used to advantage for this purpose. In this case, the holding current of the relay is adjusted to the required excitation current, independent of the operating voltage. Thereby, it is possible to appropriately reduce the control power of the relay.

From DE 10 2005 000 000 A1 an intelligent relay system is known which comprises at least relays, sensors and a control device. The relay system is adapted to detect external vibrations to which the intelligent relay system may react accordingly.

U.S. Patent Application Publication No. 2006/0007627

SUMMARY OF THE INVENTION The object of the present invention is to provide a circuit arrangement for operating at least one relay of the type mentioned at the outset, which makes it possible to further reduce the power losses of the relay and thereby reduce the heat loss. be.

A solution to this problem provides a circuit arrangement having the features of the characterizing part of claim 1 . The dependent claims relate to advantageous further aspects of the invention.

According to the invention, the circuit arrangement comprises at least one sensor means, the sensor means being adapted to detect vibrations, shocks or vibrations acting on the relay, and sensor data detected by the sensor means. an evaluation unit for evaluation, in which the current controller is arranged to adjust the control current on the basis of the sensor data evaluated by the evaluation unit. The relay can preferably be a safety relay with safety contacts, as can be used in safety switchgear arrangements. By utilizing suitable sensor means, the present invention obtains information about possible shaking, shock, vibration or other disturbances externally acting on the relay and adjusts the control current through the relay coil accordingly. It is based on the idea of adjusting If the relay is not subjected to shaking, shock, vibration, or other similar external disturbances, the risk of vibration-induced damage to the relay contacts is relatively low, and therefore the relay should be operated with a small control current. is possible, and power loss can be reduced. When the relay is subjected to jolts, shocks, vibrations, etc., the risk of vibration-induced damage to the relay contacts increases, so it is preferable to operate the relay coils at higher control currents. Dynamic, on-demand adjustment of the control current of the relay coils provides considerable advantages for lowering relay power losses. If shaking, vibration or similar disturbances affecting the relay are permanently detected and the control current is correspondingly post-adjusted, a reduction of the control current up to 50% of the manufacturer's specification is possible. That has been shown by tests. The current controller preferably constitutes a P (proportional) I (integral) controller in which the sum of the control deviations is guided such that the control deviation ends up being zero. The PI controller is thereby advantageously permanently free of control deviations.

Preferably, the sensor means and the evaluation unit can be integrated in the relay. In that respect, there is a particular structural advantage. Furthermore, the sensor means and the evaluation unit do not have to be constructed externally.

In a preferred embodiment, the sensor means are configured as acceleration sensor means, which are configured to detect acceleration acting on the at least one relay in at least one spatial direction. Such a uniaxial acceleration sensor means is sufficient in many cases. This (one) spatial direction can in particular be correlated with the axis of the relay anchor. Acceleration acting in this direction is of particular importance. Preferably, the acceleration sensor means may be a microelectromechanical system (MEMS). For certain applications, for example, two relays must be arranged at right angles to each other. Considering these circumstances, in a particularly preferred embodiment, the acceleration sensor means detects acceleration acting on at least one relay in at least two spatial directions, preferably in three spatial directions. can be configured. The acceleration sensor means can in particular be arranged on a conductive plate of the circuitry (preferably in spatial proximity to the relay).

In further embodiments, for example, the acceleration sensor means may be implemented as a 9-axis sensor and include a gyroscope and a magnetometer. This embodiment allows a particularly precise determination of the acceleration acting on the at least one relay.

In a particularly preferred embodiment, the acceleration sensor means have a sampling rate reaching at least 1 kHz, preferably at least 3 kHz, especially at least 5 kHz. A high sampling rate and data rate enables a rapid assessment of the actual operating condition of the at least one relay with respect to possible shaking, shock, vibration or other disturbances. In this sense, it can be seen that it is particularly preferable that the sampling rate of the acceleration sensor means is 5 kHz. In addition to the current controller, this circuit configuration requires a change in the control current via the relay coil, whether or not control intervention is required, evaluated at a sampling rate of 5 kHz and thus at 200 μs. Hardware and software are incorporated that are capable of performing

Preferably, the electronic switch may be a bipolar transistor. This embodiment allows a particularly robust design of the electronic switch.

In a preferred embodiment, the evaluation unit is constructed such that it is possible to determine the jerk prevailing in the area of the relay by means of the time derivative of the measured acceleration values. This jerk has been found to be a suitable dynamic value for detecting the effects of shock, shaking and vibration on at least one relay.

Preferably, the current control device is arranged such that the control current through the relay coil is high when j≧j _krit (j _krit is the critical threshold for jerk). Advantageously, the critical jerk thresholds, which may vary for different relay types, are retrievably storable in read-only memory.

In a preferred embodiment, the current control device is arranged such that the control current through the relay coil decays down when j<j _krit . Such damping down is done until a minimum control current I _Min is reached, which depends on the type of relay. This minimum control current I _Min may be in the range of about 50% of the holding current specified by the relay manufacturer.

In a particularly preferred embodiment, the relay coil is configurable for a coil voltage less than half the operating voltage supplied by the power supply. For example, it is possible to use a relay with a relay voltage of 9V. For an operating voltage of 24 V, the pulse width modulation duty ratio (the so-called "duty cycle") is approximately 30%. A large potential difference of 9 V to 24 V results in coil currents with high control deviations, thus making it possible to quickly reach the new set value of the control current. It is thus possible to further reduce the holding force of the relay in an advantageous manner. A relay with a relay voltage of 9 V has an even more significant advantage over that: a power failure or a drop in operating voltage below 16 V has hitherto caused damage to the safety switching devices with which the relay is equipped. rice field. However, it has become possible to operate this safety switching device properly down to 10.5V. A relay coil with a coil voltage of 9V has a larger wire thickness and is much less likely to break during the winding process, thus providing an advantage in manufacturing. The winding time is also significantly shorter, thus reducing the manufacturing costs of the relay. A thicker coil wire is obviously cheaper than a very finely made coil wire.

More particularly, the present invention is a circuit arrangement (1) for actuating at least one relay (2), comprising:
A power supply device capable of supplying an operating voltage (3) to at least one relay (2), wherein an electrical switch (4) is provided between the operating voltage (3) and ground (GND). and a power supply in which the relay coil (20) of at least one relay and the shunt resistor (5) are electrically connected in series;
A current control device (60), wherein the electrical switch (4) is in particular capable of being controlled with pulse width modulation and is capable of controlling the control current through the relay coil (20). and
The circuitry (1) comprises at least one sensor means, the sensor means being adapted to detect vibrations, shocks or vibrations acting on the relay (2) and the sensor means (8) detecting an evaluation unit (62) for evaluation of the sensor data obtained, in which the current controller (60) adjusts the control current based on the sensor data evaluated by the evaluation unit (62). It is a circuit configuration (1) characterized by being configured as follows.

In the present invention, the sensor means are configured as acceleration sensor means (8), which are configured to detect the acceleration acting on the at least one relay (2) in at least one spatial direction. It is characterized by

In the present invention, the acceleration sensor means (8) are arranged to detect acceleration acting on at least one relay (2) in at least two spatial directions, preferably in three spatial directions. Characterized by

In the present invention, the acceleration sensor means (8) is characterized by being implemented as a 9-axis sensor and comprising a gyroscope and a magnetometer.

According to the invention, the acceleration sensor means (8) are characterized in that they have a sampling rate reaching at least 1 kHz, preferably at least 3 kHz, in particular at least 5 kHz.

The invention is characterized in that the electronic switch (4) is a bipolar transistor.

According to the invention, the evaluation unit (62) is constructed in such a way that it is possible to determine the jerk (j) prevailing in the area of the relay (2) by means of the time derivative of the measured acceleration values. Characterized by

In the present invention, the current control device (60) is characterized in that the control current flowing through the relay coil (20) is high when j≧j _krit (j _krit is the critical jerk threshold). do.

In the present invention, the current control device (60) is characterized in that, when j<j _krit , the control current flowing through the relay coil is attenuated and lowered.

In the present invention, the relay coil (20) is characterized by a coil voltage less than half the operating voltage (3) supplied by the power supply.

1 is a schematic diagram of a circuit arrangement 1 for controlling a relay 2, constructed in accordance with a preferred embodiment of the invention; FIG.

Further features and advantages of the present invention will become apparent from the following description of preferred embodiments, with reference to the accompanying FIG. Figure 1 of the accompanying drawings shows a schematic diagram of a circuit arrangement 1 for the control of a relay 2, constructed in accordance with a preferred embodiment of the invention.

The relay 2 may in particular be a safety relay of a safety switching device and comprises, in a known manner, a relay coil 20 with a ferromagnetic core, a movable ferromagnetic anchor and one or more associated with the anchor. relay contacts. The circuitry 1 comprises a voltage supply (not shown) capable of providing an operating voltage 3 . In this embodiment the voltage supply supplies an operating voltage 3 of 24 V (DC). Between the operating voltage 3 and ground GND, the electronic switch 4, the relay coil 20 of the relay 2 and the shunt resistor 5 are electrically connected in series. In this case the relay coil 20 is arranged between the electronic switch 4 and the shunt resistor 5 .

The electronic switch 4 is preferably implemented in semiconductor technology. In this case, the electronic switch 4 is a bipolar pnp transistor. The electronic switch 4 can in another embodiment be implemented as a field effect transistor (FET), for example. The circuit arrangement 1 also has a control and evaluation device 6 , which is connected to the electronic switch 4 . The control and evaluation device 6 is implemented as a microcontroller. Alternatively, the control and evaluation device 6 may be constituted by a microprocessor together with peripherals, for example.

A current control device 60 is integrated in the control and evaluation device 6 . The current control device 60 is configured to control the electronic switch 4 by pulse width modulation (PWM), so that the control current flowing through the relay coil 20 can be adjusted to a predetermined current value. . Between the relay coil 20 and the shunt resistor 5 there is a tap 7 connected to an A/D converter 61 of the control and evaluation device 6 . A control and evaluation device 6, in particular a current control device 60 incorporated therein, is able to measure the voltage across the shunt resistor 5 via the tap 7 and determines the control current through the relay coil 20. It is configured so that

By means of the current control device 60 described above, it is possible in principle, for example, to independently control the control current through the relay coil 20 from the actuation voltage 3 to the nominal value of the holding current for the relay contacts of the relay 2. is. The electrical holding force of the relay 2 can thus be pre-lowered in an advantageous manner. However, in such a relationship, it would be desirable to be able to further reduce the electrical holding force of the relay 2 . In any case, if the control current, and thus the electrical holding force, is adjusted to a very small value, the relay contacts of relay 2 may be affected by vibration, shock, shaking or other external disturbances. , is a problem. To solve this problem, the circuit arrangement 1 described here also has at least one acceleration sensor means 8 which is connected to the control and evaluation device 6 . The control and evaluation device 6 incorporates an evaluation unit 62 for evaluating the acceleration information provided by the acceleration sensor means 8 . The goal is to quickly and precisely detect swings acting momentarily on the relay 2, which can lead to wear of the relay contacts. Preferably, the acceleration sensor means 8 are arranged to be able to measure the acceleration acting on the circuit arrangement 1 and thereby also on the relay 2 at a sampling rate of 5 kHz. The evaluation unit 62 obtains acceleration measurements from the acceleration sensor means 8 at each 200 μs time interval.

The acceleration sensor means 8 are arranged to measure acceleration in at least one spatial direction. This spatial direction can in particular be correlated with the axis of the relay anchor. This is because accelerations acting in this direction are of particular importance. A three-axis acceleration sensor means 8 capable of measuring acceleration in three mutually orthogonal spatial directions has proven to be particularly advantageous. Advantageously, the acceleration sensor means 8 may be a Micro-Electro-Mechanical System (MEMS). According to a further advantageous development, the acceleration sensor means 8 may be implemented with nine axes and may comprise gyroscopes and magnetometers. A particularly accurate acceleration measurement is thereby obtained.

The evaluation unit 62 is constructed in such a way that it is possible to determine the momentarily prevailing jerk j within the relay 2 by means of the time derivative of the measured acceleration values. The evaluation unit 62 incorporates for this purpose a suitable evaluation algorithm, which can determine the jerk j by forming the first time derivative of the acceleration. The control and evaluation device 6 includes a readable, read-only memory 63 in which important, relay-specific jerk thresholds j _krit are stored retrievably.

When j≧j _krit , the control current flowing through the relay coil 20 is increased by the current controller 60, so that the electrical holding force is increased. This makes it possible to effectively prevent wear of the relay contacts due to the action of shocks, shaking or vibrations. On the other hand, when j<j _krit , the control current flowing through the relay coil 20 is reduced by the current control device 60, so the holding force is reduced. The reduction in control current occurs up to the relay-specific minimum allowable holding current I _Min . It is not allowed to go below the minimum allowable holding current. When jerk j reaches or exceeds the critical jerk threshold _{j_krit} , the current through relay coil 20 rises again. In this connection, it should be noted that the relay coil 20 resists current changes due to self-inductive effects. The time constant τ=R/L (where R is the electrical resistance and L is the inductance) of the relay coil 20 is not linear and also depends on the magnitude of the current flowing through the relay coil 20 . In this case, the current controller 60 constitutes a PI controller, for which the addition of the control deviations results in a final control deviation of zero. Advantageously, the PI controller therefore has no control deviations permanently.

It has turned out to be advantageous to use a relay 2 with a relay coil 20 which is operated at a relay voltage which is clearly less than half the operating voltage 3 (24 V in this case). For example, relay 2 can be used with a relay voltage of 9V. For an operating voltage of 24 V, the pulse width modulation duty ratio (the so-called "duty cycle") is approximately 30%. When detecting a jerk j with j≧j _krit , the pulse width modulation is set to 100%, so it is possible to induce a large current change with an electrical actuation voltage of 24V and a relay voltage of 9V. If the jerk j is j≧j _krit , the current through the relay coil 20 is timely increased by setting the pulse width modulation to 100% or turning it fully on. Such a jerk therefore leads to a control deviation, which the current controller 60 immediately corrects. Upon reaching a current setpoint that does not cause wear of the relay contacts of relay 2 in the event of shock, shaking or vibration, the current is readjusted to a smaller value of pulse width modulation.

Such a circuit configuration 1 allows the control current through the relay coil 20 to be significantly lower than the manufacturer's specifications without compromising operational stability. As a result, the power loss, and thus the associated waste heat of the relay 2, can also be significantly reduced without associated damage associated with shaking, shock or vibration. Studies have shown that it is possible to reduce the control current to a value that is approximately 50% of the holding current value specified by the manufacturer, thus significantly reducing the self-heating of the relay 2 .

1 circuit configuration 2 relay 3 operating voltage 4 electronic switch 5 shunt resistor 6 control and evaluation device 7 tap 8 acceleration sensor means 20 relay coil 60 current control device 61 A/D converter 62 evaluation unit 63 read-only memory

Claims (7)

A circuit arrangement (1) for actuating at least one relay (2), comprising:
A power supply device capable of supplying an operating voltage (3) to at least one relay (2), wherein an electrical switch (4) is provided between the operating voltage (3) and ground (GND). and a power supply in which the relay coil (20) of at least one relay and the shunt resistor (5) are electrically connected in series;
A current control device (60), wherein the electrical switch (4) is in particular capable of being controlled with pulse width modulation and is capable of controlling the control current through the relay coil (20). and
The circuitry (1) comprises at least one sensor means, the sensor means being adapted to detect vibrations, shocks or vibrations acting on the relay (2), and the sensor means (8) detecting an evaluation unit (62) for evaluation of sensor data obtained from
The sensor means are configured as acceleration sensor means (8) adapted to detect acceleration acting on the at least one relay (2) in at least one spatial direction. ,
the evaluation unit (62) is adapted to be able to determine the jerk (j) prevailing in the area of the relay (2) by means of the time derivative of the measured acceleration values,
a current controller (60) configured to adjust the control current based on the jerk (j) determined by the evaluation unit (62) ;
The current _control device (60) has a circuit configuration ₍ 1). characterized in that the acceleration sensor means (8) are arranged to detect the acceleration acting on the at least one relay (2) in at least two spatial directions, preferably in three spatial directions, Circuit arrangement (1) according to claim 1. Circuit arrangement (1) according to claim 1 or 2, characterized in that the acceleration sensor means (8) is implemented as a 9-axis sensor and comprises a gyroscope and a magnetometer. Circuit arrangement (1) according to any one of the preceding claims, characterized in that the acceleration sensor means (8) has a sampling rate amounting to at least 1 kHz, preferably at least 3 kHz, in particular at least 5 kHz. . Circuit arrangement (1) according to any one of the preceding claims, characterized in that the electronic switch (4) is a bipolar transistor. The current control device (60) according to any one of claims 1 to 5, characterized in that the control current flowing through the relay coil is damped and reduced when j<j _krit . Circuit configuration as described (1). A circuit arrangement (1) according to any one of claims 1 to 6 , characterized in that the relay coil (20) is at a coil voltage less than half the operating voltage (3) supplied by the power supply. 1).

Images